Hospital epidemiologic surveillance for invasive aspergillosis: patient demographics and the utility of antigen detection

OBJECTIVE

To monitor the epidemiology of invasive aspergillosis at a university hospital during a period of hospital construction. To compare the efficacy of active epidemiologic surveillance for invasive aspergillosis using Aspergillus cultures with the efficacy of surveillance using Aspergillus antigen detection.

DESIGN

A prospective surveillance study.

SETTING

An 850-bed, tertiary-care, university-based hospital.

PATIENTS

A convenience sample of 153 patients with Aspergillus antigen testing and culture.

RESULTS

24 cases were identified over a 12-month period; 7 were nosocomial, and 17 were community-acquired. Cases occurred primarily in patients with hematologic malignancy, but also occurred in patients with solid tumor, steroid treatment, cardiac transplant, and acquired immunodeficiency syndrome. Culture techniques identified only 14 (58%) of 24 cases, whereas Aspergillus antigen was positive in 19 (79%) of 24 cases tested. Epidemiological surveillance using either antigen or culture positivity detected 22 (92%) of 24 cases. In addition, antigen detection was 98% specific for the detection of aspergillosis, as compared to 91% for culture and 88% for antigen and culture combined.

CONCLUSIONS

Hospital surveillance for aspergillosis should include determination of whether cases are nosocomial or community-acquired, because many may be the latter. Patients at risk for aspergillosis include patients without hematologic malignancies. Enhanced case detection occurred with active surveillance of patients considered to be at risk using both fungal serology and traditional microbiological techniques. Antigen detection was more sensitive and specific for the detection of invasive aspergillosis and may improve epidemiological surveillance for aspergillosis.

Efficacy of UK-109496, a new azole antifungal agent, in an experimental model of invasive aspergillosis

The efficacy of UK-109496, a new azole antifungal agent, was evaluated in an immunosuppressed, temporarily leukopenic rabbit model of invasive aspergillosis. Oral therapy with UK-109496 at a dosage of 10 or 15 mg/kg of body weight every 8 h was begun 24 h after a lethal or sublethal challenge, and results were compared with those for amphotericin B therapy and untreated controls. UK-109496 eliminated mortality and also reduced the tissue burden of Aspergillus fumigatus 10- to 100-fold in liver and kidney tissues and to a lesser degree in lung tissue, and at the higher dose, no viable organisms were recovered from brain tissue from these animals. Both dosages of UK-109496 decreased or eliminated circulating antigen. The half-life of UK-109496 in rabbits was 2.5 to 3 h, and no accumulation of drug was seen even after 15 doses in either uninfected or infected animals. Thus, UK-109496 shows activity in this rabbit model of invasive aspergillosis. Additional studies are needed to determine the potential of the drug for use in the treatment of this infection.

Aspergillus antigen detection in the diagnosis of invasive aspergillosis

The utility of serum Aspergillus antigen in invasive aspergillosis was determined by identifying patients with >50 ng/mL Aspergillus carbohydrate antigen by ELISA. Patients were identified from a university hospital over a 65-month period. Nineteen patients with antigenemia had proven invasive aspergillosis, 16 had probable invasive aspergillosis, and 14 had an indeterminate diagnosis. There were 5 patients with false-positive results. Antigen levels were higher in disseminated infection than in invasive pulmonary aspergillosis (median levels, 500 and 121 ng/mL, respectively). Survival also correlated with antigenemia. Serial samples were obtained from 31 of 35 patients with proven or probable invasive aspergillosis. Fifteen of 19 patients with rising or persistent antigenemia died, whereas only 1 of 12 patients who cleared antigenemia died. Higher antigen levels were useful in predicting disseminated disease, and the course of antigenemia correlated with clinical outcome. Antigen detection may be a useful addition in the management of invasive aspergillosis.

Combination therapy in experimental invasive aspergillosis

Combination antifungal therapy was assessed in an immunosuppressed rabbit model of invasive aspergillosis. Treatment with fluconazole, amphotericin B, or a combination of both significantly prolonged survival of animals lethally challenged with Aspergillus fumigatus. High-dose amphotericin B was the most effective therapy for invasive aspergillosis. Although no antagonism was seen when fluconazole was given prophylactically or therapeutically in combination with amphotericin B, combination therapy did not augment the antifungal activity of amphotericin B. Animals given a sublethal challenge of A. fumigatus had lower mortality rates when given amphotericin B, fluconazole as treatment or prophylaxis, or various combination therapies. Only animals treated with flucytosine had mortality rates comparable to those of controls. No antagonism was observed with combinations of fluconazole and amphotericin B, flucytosine and amphotericin B, or fluconazole and flucytosine. These observations provide evidence that fluconazole, flucytosine, and amphotericin B used in various combinations are not antagonistic and may provide some insight into the treatment of invasive aspergillosis in humans.

Saperconazole therapy in a rabbit model of invasive aspergillosis

The efficacy of orally and intravenously administered saperconazole against Aspergillus fumigatus was assessed in an immunosuppressed temporarily leukopenic rabbit model of invasive aspergillosis and compared with that of amphotericin B. Oral saperconazole at dosages of 5, 10, and 15 mg/kg of body weight per day improved survival compared with that of controls. In addition, saperconazole at 10 and 15 mg/kg/day reduced the tissue burden and reduced levels of circulating antigen, which correlated with increasing dosages of saperconazole. Intravenous saperconazole produced levels in serum more than 10-fold that of oral therapy. Intravenous saperconazole not only improved survival and reduced antigen levels but also significantly eradicated A. fumigatus from tissues compared with those of controls and was as effective as amphotericin B in these studies. Saperconazole was effective in the treatment of experimental invasive aspergillosis and demonstrates the potential of the newer azoles in therapy for invasive aspergillosis.

Animal models: usefulness for studies of fungal pathogenesis and drug efficacy in aspergillosis

This review describes our experience during the past 8 years with an immunocompromised rabbit model of invasive aspergillosis. We have used the model to evaluate the efficacy of a variety of antifungal therapies, including amphotericin B-deoxycholate, a liposomal amphotericin B preparation, some of the newer azoles (i.e., fluconazole, saperconazole, and the experimental compound SCH 39304), and combination therapy with amphotericin B-deoxycholate plus fluconazole. The model provides a rigorous test of efficacy when animals receive a lethal challenge; permits studies of the kinetics of aspergillar antigenemia in response to therapy with each antifungal agent or regimen; allows comparison of the relation of antigenemia to the extent of disease in target organs; and is useful in correlating the timing of antifungal therapy with the success of treatment. These observations in our animal model may provide some insight into the treatment of invasive aspergillosis in humans.

Efficacy of SCH 39304 in treatment of experimental invasive aspergillosis

The efficacy of SCH 39304 (SCH) against Aspergillus fumigatus was assessed with an immunosuppressed, temporarily leukopenic rabbit model of invasive aspergillosis. Therapy with SCH at 10 or 15 mg/kg of body weight per day was begun 24 h after lethal challenge and compared with therapy with amphotericin B at 1.5 mg/kg/day. Compared with untreated controls, SCH reduced mortality and also reduced the tissue burden of A. fumigatus 100- to 1,000-fold in liver, kidney, and lung tissues. SCH at 15 mg/kg/day and amphotericin B eliminated A. fumigatus in liver, kidney, and lung tissues. In addition, both dosages of SCH significantly eliminated the organism from brain tissues, compared with controls. Both SCH and amphotericin B decreased or eliminated circulating aspergillus antigen. These results show that new azoles can be as effective as amphotericin B in eradicating the organism from tissues and offer promise in improving the treatment of invasive aspergillosis.

The role of fluconazole in the early treatment and prophylaxis of experimental invasive aspergillosis

The efficacy of fluconazole against Aspergillus fumigatus was assessed in an immunosuppressed temporarily leukopenic rabbit model of invasive aspergillosis. Therapy with fluconazole at 60 or 120 mg/kg/day was begun 24 h after lethal challenge and compared to that with amphotericin B at 1.5 mg/kg/day. Fluconazole reduced mortality compared with that in untreated controls and at 120 mg/kg/day reduced the tissue burden of A. fumigatus 10- to 100-fold in liver, kidney, and lung. However, amphotericin B was more effective in sterilizing tissues. Both fluconazole and amphotericin B dramatically decreased or eliminated circulating aspergillus antigen. Prophylaxis with fluconazole, begun 48 h before sublethal challenge, sterilized liver and kidney tissues and significantly reduced the tissue burden in lung. Early treatment with fluconazole reduced mortality and reduced antigenemia but did not sterilize tissues. Fluconazole prophylaxis at these doses prevented dissemination of invasive aspergillosis. Fluconazole was shown to have activity in the early treatment and prophylaxis of experimental invasive aspergillosis.

Efficacy of fluconazole in experimental invasive aspergillosis

The efficacy of fluconazole against Aspergillus fumigatus was evaluated in an immunosuppressed, temporarily leukopenic rabbit model of invasive aspergillosis. Fluconazole was given at a dosage of 60 mg/kg twice daily and was compared with amphotericin B given intravenously at a dosage of 1.5 mg/(kg.d). Fluconazole reduced the tissue burden of Aspergillus from that in untreated controls by 10- to 100-fold in liver, kidney, and lung. However, at these doses amphotericin B was more effective in sterilizing tissues and in reducing the tissue burden of Aspergillus in those organs. Both fluconazole and amphotericin B decreased or eliminated circulating Aspergillus antigen and improved survival over that of untreated controls. Thus fluconazole shows activity in this rabbit model of invasive aspergillosis and should be further evaluated for use in the treatment of this disease.

Treatment of experimental invasive aspergillosis with novel amphotericin B/cholesterol-sulfate complexes

An immunosuppressed rabbit model of invasive aspergillosis was used to evaluate a novel micellar preparation of cholesterol sulfate complexed to amphotericin B. The acute LD50 of amphotericin B-deoxycholate was 5.1 mg/kg versus 20 mg/kg for the amphotericin/cholesterol-sulfate complexes. Amphotericin B-deoxycholate given iv at a dose of 1.5 mg/kg was more effective in sterilizing liver and kidney than the amphotericin/cholesterol-sulfate complexes given iv at 1.5-4.5 mg/kg, but infection persisted in the lungs of all rabbits treated with those doses. Infection persisted even when the rabbits were given a lethal dose of amphotericin B-deoxycholate (4.5 mg/kg), but a dose of 15 mg/kg of the amphotericin/cholesterol-sulfate complexes sterilized tissues and was associated with no acute lethality. Equivalent doses of the amphotericin/cholesterol-sulfate complexes were less effective than amphotericin B-deoxycholate, but a fourfold decrease in acute lethality improved the therapeutic index of amphotericin B. The amphotericin/cholesterol-sulfate complexes appear to be an improved means of amphotericin B delivery and may improve therapy for invasive aspergillosis.

Effect of immunosuppression and amphotericin B on Aspergillus antigenemia in an experimental model

A modified enzyme-linked immunosorbent assay (ELISA) for crude carbohydrate antigen was used to evaluate the kinetics of aspergillus antigenemia and to determine the effect of therapy on circulating antigen levels in an experimental model. The ELISA was rapid, simple to perform, and able to detect less than 10 ng of antigen/mL of serum. The model was also used to evaluate the effect of temporary and persistent immunosuppression on experimental disease. Antigen levels rose progressively in untreated control rabbits; all 15 animals had significant antigenemia. Treated animals had markedly reduced antigen levels, but nine of 13 rabbits had detectable antigen after 72 h of therapy, a result that correlated with persistent disease. Therapy begun 24 h after challenge in temporarily immunosuppressed animals was more likely to sterilize tissues than was therapy begun 48 h after challenge. Therapy in persistently immunosuppressed rabbits was less effective and may require improved antifungal regimens to be successful.

Comparative efficacy of ciprofloxacin, azlocillin, and tobramycin alone and in combination in experimental Pseudomonas sepsis

Ciprofloxacin, azlocillin, and tobramycin, used alone and in combination, were studied in a model of lethal pseudomonas sepsis in rats. Ciprofloxacin alone at all doses studied and tobramycin alone at the highest dose reduced mortality significantly compared with saline controls. In contrast, survival was not improved with either azlocillin alone at all doses studied or lower doses of tobramycin alone. The combination of ciprofloxacin and azlocillin was synergistic in rats with systemic pseudomonas infection. Ciprofloxacin was rapidly absorbed, and effective levels persisted for 1-4 hr relative to the dose administered. These data suggest that ciprofloxacin may be a potent agent, either alone or in combination with azlocillin, in the treatment of severe pseudomonas infections.

The diagnosis of invasive aspergillosis by an enzyme-linked immunosorbent assay for circulating antigen

An inhibition enzyme-linked immunosorbent assay (ELISA) capable of detecting 10 ng of aspergillus carbohydrate antigen/ml of serum was developed. When retrospectively applied to the sera of 19 patients with invasive aspergillosis, the ELISA detected antigen in 11 patients. None of 14 healthy controls or 28 patients with a variety of other infections were positive for circulating antigen. A rabbit model of invasive aspergillosis was also developed. Daily fungal cultures of blood were negative in the rabbits, as in human disease, but antigen was detected in increasing amounts up to the time of death. This ELISA is a sensitive, specific, and easily performed assay for circulating aspergillus antigen that should facilitate early diagnosis of invasive aspergillosis, heretofore, seldom made without invasive tests.

An experimental model to determine the level of antibiotics in irradiated tissues

An experimental study was designed using male Sprague-Dawley rats treated with a single dose of 1800 rads to an area of skin and soft tissue of the back measuring 2 X 3 cm. This dose was estimated to produce changes equivalent to 6000 rads in divided doses over 6 weeks. At intervals of 5, 10, and 15 weeks after irradiation, punch biopsies were taken from both irradiation, and nonirradiated skin areas of each animal 30 minutes after the intraperitoneal administration of gentamicin. Skin homogenates were prepared, and the antibiotic levels in these samples were determined by a bacterial growth inhibition assay. The antibiotic levels were found to be equal (16.1 +/- 6 micrograms/ml vs. 16.0 +/- 5 micrograms/ml) in both irradiated and nonirradiated skin at 5 weeks after radiation. However, at 10 and 15 weeks after radiation, the antibiotic levels had dropped to 9.9 +/- 3 micrograms/ml in irradiated skin compared with 14.1 +/- 4 micrograms/ml in normal skin (p less than 0.001) and with 5.4 micrograms/ml in irradiated skin vs. 11.8 +/- 5 micrograms/ml in nonirradiated skin (p less than 0.001), respectively. Results demonstrate that in spite of adequate gentamicin levels in the circulation and nonirradiated tissue in rats, gentamicin has a decreasing ability to diffuse into irradiated tissues with increasing intervals after therapeutic doses of radiation.

Tubulointerstitial nephritis in rabbits challenged with homologous Tamm-Horsfall protein: the role of endotoxin

Tubulointerstitial nephritis developed in 25 of 34 (74%) rabbits challenged intravenously for 2-20 weeks with adjuvant and endotoxin free homologous Tamm-Horsfall protein (THP). Lesions were characterized by focal mononuclear cellular infiltrates and microscopic scarring localized to distal nephron segments identified as thick ascending limb of the loop of Henle. Interstitial deposits of THP were found in the kidneys of more severely affected rabbits and metabolic studies demonstrated transient polyuria and tubular dysfunction. Elevations in serum IgG antibody against THP were detected in seven of 34 challenged rabbits. Tubulointerstitial nephritis was found in six of the seven rabbits with elevated antibody as well as in 19 of 27 rabbits without elevated antibody. By contrast, peripheral lymphocytes from eight of 13 rabbits with tubulointerstitial nephritis were cytotoxic against target fibroblasts in the presence of THP as compared to none of eight age matched challenged or unchallenged rabbits with normal kidneys. The presence or absence of endotoxin in vitro did not influence determinations of antibody- or lymphocyte-mediated cytotoxicity. These observations suggest that the tubulointerstitial nephritis which develops in rabbits challenged with THP is primarily the result of cell-mediated immune responses directed against THP, and does not require the presence of endotoxin in the challenge solution, or serum IgG antibodies directed against THP.

Immunopathogenesis of chronic pyelonephritis

Immunopathologic responses to urinary Tamm-Horsfall protein in the development of chronic pyelonephritis were examined by four different approaches. First, in a rabbit model, tubulointerstitial nephritis developed in 64 of 102 rabbits injected intravenously with urine or rabbit Tamm-Horsfall protein as compared with only one of 17 rabbits in two control groups. Circulating cytotoxic lymphocytes plus immunoglobulin G (IgG) antibodies against Tamm-Horsfall protein were found in 51 percent of challenged (urine or Tamm-Horsfall protein) rabbits with tubulointerstitial nephritis as compared with only 8 percent of those without it (p less than 0.001). Second, in a porcine model of reflux nephropathy, 16 of 21 pigs with pyelographic findings indicative of reflux had elevated serum titers of anti-Tamm-Horsfall protein antibody as compared with 0 of 13 with normal pyelograms. Five of 10 refluxing pigs tested also had circulating lymphocytes that were cytotoxic in the presence of Tamm-Horsfall protein as compared with 0 of 13 with normal pyelograms. Third, in human studies, 12 of 49 patients with recurrent nephrolithiasis demonstrated abnormal elevations in anti-Tamm-Horsfall protein antibody; 13 of 49 had an abnormality in one of two assays of cell-mediated immunity to Tamm-Horsfall protein as compared with 0 of the normal control subjects. These abnormalities were not associated with overt obstruction or bacteriuria, but appeared to be more common in patients with recent onset and active recurrent nephrolithiasis. Lastly, an inhibitor of the binding reaction between human Tamm-Horsfall protein and its IgG antibody was detected in extracts of three uropathic coliforms. The inhibitors were partially purified by chromatographic means. Preliminary immunoautoradiographic studies revealed three or less protein-containing subunits of Escherichia coli that cross-reacted with anti-Tamm-Horsfall protein antibody. These studies suggest that autoimmune responses to Tamm-Horsfall protein may occur after exposure to Tamm-Horsfall protein by intravenous challenge, urinary reflux, or recurrent nephrolithiasis. This autoimmune response to Tamm-Horsfall protein may be the pathogenetic mechanism by which these factors, including bacteriuria, contribute to chronic pyelonephritis.

The BF locus and HLA: rare alleles coding for functionally active and inactive factor-B products

The genetic polymorphism of properdin factor B (BF) was studied in different populations. The rarer alleles, BF*F1 and BF*S1, occurred in Caucasians, were less frequent in North American blacks, and were not demonstrated in any of three Oriental populations studied. Two further alleles of BF, termed BF*FM and BF*SM, were found to exist in these populations. The BF*FM allele, which was found only in Caucasians, codes for a functionally inactive factor-B product, whereas the BF*SM allele (found in a single Chinese individual), like other alleles of BF, codes for a functionally active product. HLA haplotype analyses in individuals carrying the rarer alleles of BF revealed not only a strong association between BF*F1 and HLA-B18 and BF*S1 and HLA-Bw50 but an even stronger association between these BF alleles and alleles of the two C4 loci. BF*F1 occurred most frequently on a C4A*3,B*Q0 haplotype, whereas the BF*S1 allele was usually found on a C4A*2,B*1/B*Q0 haplotype. HLA haplotypes carrying the BF*FM and BF*SM alleles all carried the more common C*4A3,B*1 haplotype.

HLA-linked genetic markers in Chinese and other Oriental populations

The polymorphic variants of the HLA-linked genetic markers Bf, C2, C4 and GLO-I were studied in three mongoloid populations. Analysis of linkage dis-equilibrium between these markers and HLA-A, B, C and DR antigens was carried out on test results from 140 unrelated Chinese individuals. The phenotypes BfS and GLO-2 were found at significantly higher frequencies than in Caucasians. BfS was associated with B12 in Japanese but not in Chinese. A single individual with the rare Bf variant S1 was found. No C2 deficient individuals were observed. The C2C (common) allele occurred at a gene frequency of 0.949 and the more basic allele C2B at 0.039. The acidic variant, C2A, was observed at a frequency of 0.011 and appeared to be associated with BfF. Eighty-nine per cent of the Chinese were phenotypically C4FS. In contrast to Bf and C2, each of which is coded for by codominant alleles at a single genetic locus, C4 is coded for by two genes, C4F (Rodgers) and C4S (Chido). The C4F locus allele, C4F1 (extra fast), was strongly associated with HLA-B17, as has been found in other populations, but a new association of the C4S locus deficiency allele, C4so (Ch-), with B17 was also observed. All HLA-B17;C4so haplotypes were BfS position. As has been previously found in Caucasian populations, individuals of the C4F phenotype (i.e. genotypically FsoFso) were all found to be Chido negative. The frequencies of the various HLA-linked genetic markers, however, as much as the frequencies and associations of the HLA antigens themselves, distinguish these populations from other ethnic groups.

Different HLA antigen associations for the functionally active and inactive products of the complement C4F1 allele

The genetic polymorphism of the fourth component of human complement, C4, was studied in 945 unrelated Caucasian individuals. A third allele of the C4F (Rodgers) locus, termed C4F1 was demonstrated. This allele is characterized using immunofixation electrophoresis, by the presence of an additional fast-moving anodal band of C4 which distinguishes it clearly from the common C4F variant. The allelic frequencies fit the Hardy-Weinberg equilibrium assuming three alleles at the C4F locus: C4F, C4Fo, and C4F1. The functional activity of the C4F variants was investigated using a specific hemolytic overlay technique for C4. It was found that in almost all individuals (75 out of 78), the C4F1 allele codes for a functionally inactive C4 product only when it occurs on an HLA-B17 positive haplotype but that the same allele codes for a functionally active fast variant of C4 when it occurs on an HLS-B37 positive haplotype (18 out of 18). Very strong genetic linkage disequilibrium was observed for the C4F1 allele with HLA-B17 and B37. The active and inactive C4F1 variant also has marked nonrandom gametic association to different alleles of the Bf locus and to HLA-C locus determinants. No further variants of the C4S (Chido) locus have been identified so far. Rodgers (Rg) typing by the plasma inhibition test of anti-Rg antiserum has shown that plasma from individuals homozygous for the C4F1 allele is only able to partially inhibit anti-Rg whereas all C4F positive individuals totally inhibited the reaction.